Explanation:
What does our Milky Way Galaxy look like from afar?
Since we are stuck inside, and since opaque
dust truncates our view in
visible light, nobody knows for sure.
Drawn above, however, is a good guess based on many different types of observations.
In the Milky Way's centre
is a very bright core region centred on a
large black hole.
The Milky Way's bright
central bulge
is now thought to be an
asymmetrical bar
of relatively old and red stars.
The outer regions are where the
spiral arms
are found, dominated in appearance by
open clusters
of young, bright, blue stars, by red
emission nebula, and by dark dust.
The spiral arms reside in a disk dominated in mass by relatively dim stars and
loose gas composed mostly of
hydrogen.
What is not depicted is a huge spherical halo of invisible
dark matter that dominates the mass of the
Milky Way
as well as the motions of stars away from the centre.